The noise and vibration associated with the recent development of the modes of transportation such as automobiles have become serious social problems. Further, there have been sophisticated needs that the vibration and noise experienced inside automobiles be reduced. Furthermore, the use of office machines such as copiers and printers has expanded to ordinary households, and the reduction of the noise and vibration generated by these machines has become an important challenge. Still further, home electric appliances have been enlarged to meet changes in lifestyle, and the quietness by reducing the vibration and noise of appliances that vibrate such as refrigerators, washing machines and vacuum cleaners is one of the important performances of the products.
A conventional approach to reducing such vibration and noise is to use various insulators such as springs and vibration insulating rubbers. This approach aims to reduce the generation of vibration and noise by insulating the transfer of vibration, but has been unsuccessful in satisfying the various demands mentioned above.
Another method that has become increasingly widespread is the so-called vibration damping that suppresses the vibration itself from the sources such as machines. Specifically, various viscoelastic bodies as vibration dampers are applied to or inserted between the vibration sources to suppress the occurrence of vibration. For example, known vibration dampers used for this purpose are block copolymers including diene monomer blocks and aromatic vinyl monomer blocks.
However, such block copolymers sometimes fail to exhibit a sufficient vibration damping performance due to factors such as changes in ambient temperature during actual use.
Patent Literature 1 describes a vibration insulator used to insulate the vibration of lightweight instrument which includes a nonaromatic rubber softener for the purpose of decreasing the hardness of a thermoplastic elastomer such as a hydrogenated styrene-butadiene-styrene block copolymer. However, this literature is silent with respect to vibration damping properties, and studies using the softener specifically disclosed in the literature have found that the vibration damping performance is insufficient. Further, weather resistance is poor depending on the types of softeners.
Patent Literature 2 describes a resin composition including an isobutylene block copolymer and a polyolefin resin and having low hardness and high loss properties (vibration damping properties) as well as good gas permeability. This literature describes that a nonaromatic rubber softener is added in order to further decrease hardness. However, studies using the softener specifically disclosed in the literature have found that the vibration damping performance is insufficient. Further, weather resistance is not satisfactory depending on the types of softeners.